Nuclear power related facilities, etc., produce many articles to be taken out and waste of various shapes. The former includes apparatuses, equipment, scaffolding, etc. which were used in a controlled area, and the latter includes waste produced when aging facilities are remodeled or dismantled. It is mandatory to classify these articles and waste according to their radioactivity levels so that they are subjected to predetermined processing such as disposal or storage. For this purpose, the presence/absence and the level of radioactive contamination of waste are measured using various radioactivity measuring apparatuses. In this case, a surface contamination survey meter is widely used to measure surface contamination by measuring the entire surface of an object to be measured.
A conventional survey meter is constructed of a probe incorporating a scintillator or gas type detector and a radioactivity measuring section provided with a calculation circuit for calculating measured values and a meter display section, etc., both of which are connected together via an electric signal cable (see, for example, Japanese Patent Laid-Open Specification No. 2001-4757).
Most of such conventional surface contamination surveymeters are of a type of meter which detects radioactive contamination of the surface of waste, but it is extremely difficult through measurements using such surveymeters to detect the presence/absence of contamination inside equipment or on the inner surface of piping, etc., and the contamination level thereof. This is because in most cases their probes are too big to be inserted inside the equipment or piping. For example, a scintillation detector needs to have a structure including a scintillator and photomultiplier, while a gas type detector (a proportional counter or a GM tube) is filled with a gas and needs to keep a certain distance between an anode electrode and a cathode electrode, and it is difficult to reduce the volume in both cases. Therefore, for objects that cannot be measured, it is necessary, for example, to cut the piping longitudinally for direct measurement, which results in considerably low efficiency in measurement work.
On the other hand, when an object to be measured is a human body, clothes or other object having two-dimensional extension, a radioactivity detection apparatus is being developed whose detection surface is expanded accordingly (see, for example, Japanese Patent Laid-Open Specification No. 9-159769/1997). The radioactivity detection section has a structure, for example, having a plate-shaped scintillator with an expanded detection surface so as to guide light generated by radiation into a photomultiplier through a wavelength conversion optical fiber, all of which are integrated as one body. Therefore, an electric signal photoelectrically converted by the photomultiplier of the radioactivity detection section is transmitted to the measuring section of the main body via an electric cable. When an object to be measured has, for example, a curved surface, such a structure must be designed according to the curved surface, which results in insufficient versatility. Furthermore, such a structure may be suitable when the object to be measured has a plate-shape and a large area, but it is difficult to narrow the shape, and such an apparatus is not suitable in a mode of use in which it is inserted inside equipment or piping.